Rotary cutting tools have come nowadays into wide-spread use as finishing tools. Rotary machining characterized by the rotary motions of the tool and workpiece about their respective axes minimizes the rate of slip in the zone of contact between the tool and the workpiece, extending this zone at the same time, and reduces the generation of heat by 30-60%. The result is good tool stability, short machine time and improved surface finish. Inherent in all rotary cutting tools are common design features such as a cutter attached to a cantilevered end of a shaft supported by a ball bearing assembly which is accommodated in a body. The spindle assembly used in the known rotary tools lacks durability and the cutter displays poor stability.
There is known a rotary cutting tool having a body with journal and thrust bearings giving support to a shaft carrying a cutter at its cantilevered end. In operation, the cutting force bends the shaft out-of-true with the axis of the journal bearing next the cutter. The line of the contact between the shaft and bearing becomes an ellipse rather than a circle and, as a result, the durability of the shaft and that of the tool as a whole is impaired. Moreover, an excessive runout of the cutter at its edges resulting from the wear on the journal bearing reduces the stability of the cutter.